The only experience I've had with DLC was a bad one. It was back in 2007, developing a specialty engine with Mahle. It was DOHC, but it had shaft-mounted finger followers to actuate the valves. Those followers were DLC coated... Anyway - the DLC flaked/chipped off, got churned into DLAD (diamond-like abrasive dust) by the oil pump and the entire engine looked like it'd had lapping compound for oil (it basically did). Total fail.
Dang that sucks.. was that on the cusp of new tech during that time? Cause dlc seems to be pretty standard in the oem motorcycle engine world nowadays. BMW s1000rr uses dlc coated finger followers for example.
@@CP110 Dunno how old DLC was at the time. It was the first I'd heard of it. The project engineer said it was the latest/greatest stuff being used in Formula 1 (this was during the era of 21,000 rpm F1 engines). I'm not trying to say DLC is junk. I'm just wary of coatings inside engines in general because coatings are prone to peeling/flaking. It's one thing if some Grafal anti-friction coating flakes off the piston skirts, but another altogether when "diamond like" stuff starts circulating...
Those look like used buckets that were DLC coated? Big nono, adhesion is an issue with DLC in the first place and oil can impregnate the surface of parts. DLC coating should ONLY be done to new parts that have been extensively cleaned. But I still believe a big issue with billet/dlc cam wear against buckets comes down to hardness differences.
Hardness doesn’t matter if it’s all working correctly. If the cam and bucket doesn’t slide with each other then something is gonna die. With the billet cam, sure it would be the bucket. On a cast cam, it’s the same. Valve float oil displacement between the bucket and cam. And if there’s oil contamination there would be an issue. But, hardness doesn’t mean anything will fail. They are simply not made to crash into each other, it’s called a follower because it’s meant to follow. And they were new buckets from a manufacturer that sells them as a dlc coated bucket. When there is an issue, like mentioned above any DLC is not going to survive it. It will just take longer to fail.
in a mechanical system hardness always matters concerning wear. Tuliping heads are hardness related failures. Valve float rapidly accelerates wear. It should clue you in to design or specification deficiencies in the setup. One thing you should keep in mind is that the actual contact surface on the valve seat is usually going to be a fraction of a square inch, meaning the actual seat pressure is some multiple of the spring rate at installed height. 80psi of “seat pressure” can easily be 320lbs across a 0.25in^2 contact surface. And millions of cycles will show wear even on what you might consider low load figures. Only the cam “should always” be on a sliding or rolling lubrication mode. There is valve lash. The seat is always slapped on, higher spring rates meaning higher acceleration rates in to the seat. Seat hardness should be close to valve hardness. OEMs are always trying to minimize valve train weight = lower spring rates = longer life. Lower load always means longer life. Most aftermarket spring kits are much stiffer than they actually need to be in most people’s run of the mill setups, in order to cover all bases. And longer life is the primary purpose of DLC, to create a hard wear resistant surface. Similar concept to a drill bit, a harder bit will cut (wear) a softer material faster.
I’m saying that someone said on RU-vid that the only way you can use a billet cam is with a DLC bucket. But I’ve been saying on RU-vid and everywhere else that it’s not the cams fault because as long as the bucket slides against the cam as it’s designed for that it won’t die. But if there’s a float issue, it’s gonna take the bucket out regardless of what you coat it with. Then the coating just chips off and goes into the engine. If it’s gonna fail, it just takes longer to fail with the DLC.
